I've never thought of crows or rooks as migratory birds. Here in the Staffordshire Moorlands they seem to hang around all year, along with the jackdaws and magpies. I'd guess that corvids are the most plentiful species around here.
It is fascinating to watch their techniques fro getting seeds and peanuts out of the bird feeders we have put up for the little birds. It's also interesting to see that they wait and take turns with no squabbling.
On the other hand, the seagulls have arrived from the coast for a warmer winter in the woods on Congleton Edge.
Cheers
Dave